Chlorohydrin and cationic compounds having high affinity for pulp or paper

ABSTRACT

Selected chlorohydrin and cationic compounds containing nitroxide or hydroxylamine moieties are effective in stabilizing pulp or paper, especially pulp or paper containing lignin, against yellowing and discoloration due to the adverse effects of light. These compounds are added at various points in the paper-making process, especially at the wet ends, making the need for water soluble or water dispersible materials having high affinity for pulp or paper essential. This performance is often further enhanced by the presence of one or more coadditives selected from the group consisting of the UV absorbers, the polymeric inhibitors, the nitrones, the fluorescent whitening agents and metal chelating agents. Combinations of hydroxylamines or their salts, benzotriazole or benzophenone UV absorbers and a metal chelating agent are particularly effective.

This application claims benefit under 35 USC 119(e) of U.S. ProvisionalApplication No. 60/154,112, filed Sep. 15, 1999.

The instant invention pertains to new chlorohydrin or cationic compoundshaving nitroxide or hydroxylamine moieties which have high affinity forpulp or paper, particularly that containing lignin, and which compoundsare useful in preventing the loss of brightness and for enhancingresistance to yellowing in pulp or paper, especially that which stillcontains lignin. This performance is often further enhanced by thepresence of one or more coadditives selected from the group consistingof the UV absorbers, the polymeric inhibitors, the nitrones, thefluorescent whitening agents and metal chelating agents. Combinations ofhydroxylamines or their salts, benzotriazole or benzophenone UVabsorbers and a metal chelating agent are particularly effective.

BACKGROUND OF THE INVENTION

High-yield and ultra-high yield wood pulps undergo rapid light-induceddiscoloration, particularly when they are exposed to near ultravioletlight (wave lengths 300–400 nm) in indoor fluorescent light anddaylight. This characteristic restricts their use to short-life,low-value paper products. High-yield and ultra-high yield wood pulps canbe bleached to a high level of whiteness. If this whiteness could bestabilized against discoloration, these bleached high-yield pulps coulddisplace significant amounts of more expensive fully-bleached, low-yieldchemical pulps.

This discoloration is ascribed to the substantial lignin content ofhigh-yield pulps totally about 20–45% by mass. Phenoxy radicals are thekey intermediates in the reaction mechanism. Several light-inducedreactions have been proposed to account for their formation such ascleavage of the aryl ether bond of phenacyl aryl ether groups, orbreakdown of ketyl radicals formed from saturated aryl-glycerol β-arylether structures in lignin. The phenoxy radicals are oxidized by otheroxygen-centered radicals (alkoxy and perhydroxy) to form yellowchromophores. (C. Heitner, “Photochemistry of LignocellulosicMaterials”, C. Heitner, J. C. Scaiano, Eds.; ACS Sym. Ser. 531, 1–25(1993).)

I. E. Arakin et al., Khymiya drevesiny (Chemistry of Wood), 1982, No. 2,114 and A. D. Sergeev et al., ibid, 1984, No. 5, 20 disclosed that theuse of iminoxyl radicals such as TEMPO(1-oxyl-2,2,6,6-tetramethylpiperidine) is useful in the delignificationof wood using the one-stage oxygen-soda (alkaline) process, but made nomention or suggestion of any activity provided by TEMPO on preventinglight-induced discoloration of paper or pulp made from such treatedwood.

EP 717,143 and WO 97/36041 describe a multicomponent system forchanging, reducing or bleaching lignin and lignin-containing materialswhich comprise an oxidation catalyst, and an N-hydroxyl mediatorcompound such as N-hydroxyphthalimide or a dialkyl-hydroxylamine. Thesereferences are aimed at the delignification of wood. There is no mentionor suggest of any activity provided by the N-hydroxyl compounds inpreventing the light-induced discoloration of paper or pulp made fromsuch treated wood.

V. I. Khodyrev et al., Vysokomol soyed, A29, No. 3, 616 (1987) [PolymerSci. U.S.S.R., 29, No. 3, 688 (1987)] show that the photoinitiatedoxidation by oxygen causes weathering of cellulosic textile materialssuch as flax or cotton, and that the light stability of the cellulosecould be improved by photostabilizers such as the UV absorbers,benzophenols and 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine. The UVabsorbers offer no protection, and are actually detrimental. The authorsnoted that the stable nitroxyl radical interacts with alkyl radicals inthe cellulose to afford its salubrious stabilizing activity. There is nosuggestion by the authors that this stabilizing activity could beapplied successfully in wood pulp and/or paper made therefrom.

M-K. Syler et al., J. Assn. Paper Pulp Tech, 29, 135 (1990) show thatselected metal salts such as magnesium sulfate and lower alkanoic acidsinhibit color reversion in bleached pulp.

P. Fornier de Violet et al., Cellulose Chem. Tech., 24, 225 (1990) showthat the use of UV absorbers and hydrogen donor agents such as thiols,ascorbic acid, etc. help prevent the photoinduced discoloration ofhydrogen peroxide bleached wood pulp, but that chain breakers such ashindered phenols and hindered amines (having >N—H or >N—CH₂— moieties)had no or even a detrimental effect on preventing photoinduceddiscoloration.

R. Agnemo et al., 6th International Symposium on Wood and PulpingChemistry, Appita, 1991, confirmed that free hydroxyl radicals pluslignin lead to undesirable photoyellowing in pulp and paper.

S. Omori et al., J. Assn. Paper Pulp Tech, 48, 1388 (1993) describes theeffect of antioxidants and UV absorbers on light reversion and concludesthat the combination of an antioxidant and UV absorber prevents colorreversion and has a synergistic effect in that activity.

M. Paulsson et al., 8th International Symposium Wood and PulpingChemistry, Helsinki, 1995, show that efficient photostabilization ofunbleached paper or hydrogen peroxide bleached TMP pulp can be achievedby acetylation.

There have been a number of different approaches proposed to inhibitingthe yellowing of mechanical pulps. These include: radical scavengers andantioxidants; UV screens; elimination of chromophores after theirformation; chemical modification of lignin by alkylation or acetylation;polymeric inhibitors; and two types of coadditives used in combination.Z-H. Wu et al., Holzforschung, 48, (1994), 400 discuss the use ofradical scavengers like phenyl-N-tert-butylnitrone to reduce theformation of chromophores during mechanical pulping and give a morelight-stable pulp.

C. Heitner, “Chemistry of Brightness Reversion and It Control, Chapter5”, in Pulp Bleaching-Principles and Practice, C. W. Dence, D. W. Reeve,Eds., TAPPI, Atlanta, 1996, pp 183–211, summarizes the state of the artin the thermal and light-induced yellowing of lignin-containing pulpssuch as thermomechanical (TMP) and chemithermomechical (CTMP) pulps,showing the seriousness of these undesirable effects discusses generallythe then current prior art methods used to attack this problem. Theseinclude bleaching, the use of phosphites, UV absorbers, polyalkyleneglycols and free radical scavengers such as ascorbic acid, thiols,thioethers, dienes and aliphatic aldehydes and chelating agents such asethylenediaminetetraacetic acid (EDTA). The author concluded that,although much progress had been made, much still remains to be donebefore a successful and practical solution to this loss of brightnessand undesirable yellowing of lignin-containing pulp and/or paper isfound.

Copending application Ser. Nos. 09/119,567; 09/234,253; 60/116,687 and60/116,688 describe potential solutions where the use of selectedhindered amine nitroxides, hindered amine hydroxylamines,N,N-dialkylhydroxyamines or their salts in combination with selected UVabsorbers and metal chelating agents is seen to prevent loss ofbrightness and to enhance resistance to yellowing in mechanical orchemical pulp or paper, particularly mechanical pulp or paper stillcontaining significant amounts of lignin.

DETAILED DESCRIPTION OF THE INVENTION

This invention involves novel chlorohydrin or cationic nitroxides,hydroxylamines or hydroxylamine salts which are water compatible andhave high affinity for pulp. These compounds, when applied to pulp whichstill contains lignin, either chemical (kraft) pulp containing littlelignin or particularly mechanical pulp containing significant amounts oflignin, either alone or in combination with UV absorbers, metalchelating agents, fluorescent whitening agents, sulfur containinginhibitors, phosphorus containing compounds, nitrones, benzofuran-2-onesand/or stabilizing polymers effectively confers light and thermalstability which is similar to that found in papers made from kraft pulp.

More particularly, the instant compounds are those of formulas I to X,or IA to XA

or a product of one of the following reactions XI to XVI or XIA to XVIA

where

-   -   k ranges from 1 to 10; n is 1 or 2; and m ranges from 2 to 6;    -   E is oxyl, hydroxyl, hydrogen, alkyl, alkyl substituted by        hydroxyl, by oxo or by carboxy, alkyl interrupted by oxygen, by        —COO— or by —OCO—, alkenyl, alkynyl, cycloalkyl, cycloalkenyl,        bicycloalkyl, alkoxy, alkoxy substituted by hydroxyl, by oxo or        by carboxy, alkoxy interrupted by oxygen, by —COO— or by —OCO—,        cycloalkoxy, alkenyloxy, cycloalkenyloxy, aralkyl, aralkoxy,        acyl, RCOO—, ROCOO—, RNCOO— or chloro where R is an aliphatic or        aromatic moiety,        when n is 1,    -   R₁ is hydrogen, alkyl of 1 to 18 carbon atoms, alkenyl of 2 to        18 carbon atoms, propargyl, glycidyl, alkyl of 2 to 50 carbon        atoms interrupted by one to twenty oxygen atoms, alkyl of 2 to        50 carbon atoms substituted by one to ten hydroxyl groups or        both interrupted by said oxygen atoms and substituted by said        hydroxyl groups, or    -   R₁ is alkyl of 1 to 4 carbon atoms substituted by a carboxy        group or by —COOZ where Z is hydrogen, alkyl of 1 to 4 carbon        atoms or phenyl, or where Z is said alkyl substituted by        —(COO⁻)_(n)M^(n+) where n is 1–3 and M is a metal ion from the 1        st, 2nd or 3rd group of the periodic table or is Zn, Cu, Ni or        Co, or M is a group N^(n+)(R₂)₄ where R₂ is hydrogen, alkyl of 1        to 8 carbon atoms or benzyl, or        when n is 2,    -   R₁ is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12        carbon atoms, xylylene or alkylene of 1 to 50 carbon atoms        interrupted by one to twenty oxygen atoms, substituted by one to        ten hydroxyl groups or both interrupted by said oxygen atoms and        substituted by said hydroxyl groups,    -   X is an inorganic or organic anion, where the total charge of        cations is equal to the total charge of anions.

The index j determines the number of cations X necessary, together withother cations described in the above formulas such as Cl—, to equal thetotal charge of anions. Thus, in formulae I to VIA, j equals n dividedby the valency of X, and in formulae VIIA to XVIA j equals the number ofammonium ions in the formula divided by the valency of X.

The instant stabilizers are conveniently obtained by reacting stericallyhindered amine educts with suitable reactants known in the art.Reactions are carried out according to or in analogy to methods known inthe art and illustrated in present examples. Suitable piperidine educts,e.g. carrying in 4-position an oxo, hydroxy, amino or carboxy group, areknown compounds. For example, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-one,1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine,1-oxyl-2,2,6,6-tetramethyl-4-aminopiperidine and1-oxyl-2,2,6,6-tetramethyl-4-carboxy-piperidine are known compounds andcan be obtained commercially (Aldrich Chemical Company).

The above hydroxypiperidylammonium compounds indicated with the letter A(formulae IA, IIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IXA, XA, XIA, XIIA,XIIIA, XIVA, XVA, XVIA) are addition salts of the corresponding compoundof the same number, without letter A, wherein E is OH, with an acidH_(1/j)X which may conveniently be prepared from these components or, asan alternative, from the corresponding hydroxypiperidylammonium compoundwith suitable reactands as described.

Preferably, X is phosphate, phosphonate, carbonate, bicarbonate,nitrate, chloride, bromide, iodide, bisulfite, sulfite, bisulfate,sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate,acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate,gluconate, malate, mandelate, tiglate, ascorbate, polymethacrylate, acarboxylate of nitrilotriacetic acid,hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraaceticacid or of diethylene-triaminepentaacetic acid, adiethylenediaminetetraacetic acid or of diethylene-triaminepentaaceticacid, an alkylsulfonate or an arylsulfonate.

More preferred X are chloride, bromide, citrate, iodide ormethylsulfate; especially preferred are chloride and bromide.

E is preferably oxyl, hydroxyl, alkoxy, alkoxy substituted by hydroxyl,oxo or carboxy or interrupted by oxygen or carboxy, cycloalkoxy,alkenyloxy, cycloalkenyloxy, aralkyl, aralkoxy, acyl, R(C═O)O—,RO(C═O)O—, RN(C═O)O— or chloro, where R is an aliphatic or aromaticmoiety.

More preferably, E is oxyl, hydroxyl, C₁–C₁₈alkoxy; C₃–C₁₈alkoxysubstituted by hydroxyl, oxo or carboxy or interrupted by oxygen orcarboxy; C₅–C₁₂cycloalkoxy; C₃–C₁₂alkenyloxy; cyclohexenyloxy; aralkylor aralkoxy of 7 to 15 carbon atoms; C₁–C₁₂acyl; R(C═O)O—, RO(C═O)O—,RN(C═O)O—, where R is C₁–C₁₈alkyl, phenyl, C₇–C₁₅phenylalkyl,cyclohexyl, C₂–C₃alkenyl. Most preferred E is oxyl, hydroxyl,C₁–C₈alkoxy or cyclohexyloxy, especially oxyl or hydroxyl.

Any alkyl group within these definitions are preferably C₁–C₁₈alkylcomprising methyl, ethyl, propyl such as n- or isopropyl, butyl such asn-, iso-, sec- and tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl,decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl,heptadecyl or octadecyl. Alkoxy is O-alkyl, preferably C₁–C₈alkoxy.Cycloalkyl usually is C₅–C₁₂cycloalkyl, preferably cyclohexyl.Alkenyloxy is usually C₃–C₁₂alkenyloxy, especially allyloxy. Aralkyl andaralkoxy usually is of 7 to 15 carbon atoms and is preferablyC₇–C₁₅phenylalkyl or C₇–C₁₅phenylalkoxy. Acyl is preferablyC₁–C₁₂alkyl-CO, especially acetyl, C₂–C₃alkenyl-CO, benzoyl. R as analiphatic or aromatic moiety is preferably C₁–C₁₈alkyl, phenyl,C₇–C₁₅phenylalkyl, cyclohexyl, C₂–C₃alkenyl.

Most preferred are compounds of formula I, IA, II, IIA, IV, IVA, VII,VIIA, VIII, VIIIA, IX, IXA, or the reaction product XI or XIA,especially those wherein

-   -   k is 1 or 2; m is 2 or 3;    -   E is oxyl, hydroxyl, or C₁–C₈alkyl;    -   R₁, when n is 1, is H or C₁–C₈alkyl, or, when n is 2, is        alkylene of 2–12 carbon atoms; and    -   X is chloride, bromide or citrate.

The instant invention also pertains to a process for preventing the lossof brightness and for enhancing resistance to yellowing of a pulp orpaper, particularly a chemimechanical or thermomechanical pulp or paperwhich still contain lignin, which comprises

-   -   treating said pulp or paper with an effective stabilizing amount        of a compound of any of formula I to XI or IA to XVIA as        described above.

The effective stabilizing amount of the compounds of formula I to XVIAis 0.001 to 5% by weight based on the pulp or paper. Preferably, theeffective stabilizing amount is 0.005 to 2% by weight; preferably 0.01to 1% by weight.

When a coadditive stabilizer is also present, the effective stabilizingamount of the coadditives is also 0.001 to 5% by weight based on thepulp or paper; preferably 0.005 to 2% by weight; most preferably 0.01 to2% by weight.

The instant compounds may additionally include an effective stabilizingamount of at least one stabilizer selected from the group consisting ofthe UV absorbers, the polymeric inhibitors, the sulfur containinginhibitors, the phosphorus containing compounds, the nitrones, thebenzofuran-2-ones, fluorescent whitening agents, hindered aminehydroxylamines and salts thereof, hindered amine nitroxides and saltsthereof, hindered amines and salts thereof, benzofuran-2-ones and metalchelating agents.

The compositions which also include a UV absorber are especiallypreferred. The UV absorber is selected from group consisting of thebenzotriazoles, the s-triazines, the benzophenones, theα-cyanoacrylates, the oxanilides, the benzoxazinones, the benzoates andthe α-alkyl cinnamates.

Preferably, the UV absorber is a benzotriazole, an s-triazine or abenzophenone, most especially a benzotriazole UV absorber orbenzophenone UV absorber.

Typical and useful UV absorbers are, for example,

-   5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;-   2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;-   2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole;-   2-(2-hydroxy-3,5-di-αcumylphenyl)-2H-benzotriazole;-   2-(2-hydroxy-3-α-cumyl-5-tert-octylphenyl)-2H-benzotriazole;-   2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole;-   2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole-5-sulfonic    acid, sodium salt;-   3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamic acid;-   12-hydroxy-3,6,9-trioxadodecyl    3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;-   octyl    3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;-   4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine    (*is mixture of C₁₂₋₁₄oxy isomers);-   4,6-bis(2,4-dimethylphenyl)-2-(4-octyloxy-2-hydroxyphenyl)-s-triazine;-   2,4-dihydroxybenzophenone;-   2,2′,4,4′-tetrahydroxy-5,5′-disulfobenzophenone, disodium salt;-   2-hydroxy-4-octyloxybenzophenone;-   2-hydroxy-4-dodecyloxybenzophenone;-   2,4-dihydroxybenzophenone-5-sulfonic acid and salts thereof;-   2-hydroxy-4-methoxybenzophenone-5-sulfonic acid and salts thereof;-   2,2′-dihydroxy-4,4′dimethoxybenzophenone-5,5′-disodium sulfonate;    and-   3-(2H-benzotriazol-2-yl)-4-hydroxy-5-sec-butylbenzenesulfonic acid,    sodium salt (CIBAFAST® W).

Other preferred compositions are those which additionally contain apolymeric inhibitor; preferably poly(ethylene glycol), poly(propyleneglycol), poly(butylene glycol) or poly(vinyl pyrrolidone).

Still other preferred compositions wherein the additional stabilizer isa sulfur containing inhibitor; preferably polyethylene glycoldithiolacetate, polypropylene glycol dithiolacetate, polybutylene glycoldithioacetate, 1-thioglycerol, 2-mercaptoethyl ether, 2,2′thiodiethanol,2,2′-dithiodiethanol, 2,2′oxydiethanethiol, ethylene glycolbisthioglycolate, 3-mercapto-1,2-propanediol,2-(2-methoxyethoxy)-ethanethiol, glycol dimercaptoacetate,3,3′-dithiopropionic acid, polyethylene glycol dithiol, polypropyleneglycol dithiol, polybutylene glycol dithiol or ethylene glycolbis(mercaptoacetate).

Other preferred compositions are those wherein the additional stabilizeris a phosphorus containing compound; preferablytris(2,4-di-tert-butylphenyl) phosphite,2,2′,2″-nitrilo[triethyl-tris(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite], bis(2,4-di-tert-butyl-6-methyl-phenyl) ethyl phosphite,sodium hydroxymethyl phosphinate, tetrakis(2,4-di-butylphenyl)4,4′-biphenylenediphosphonite, tris(nonylphenyl) phosphite,bis(2,4-di-tert-butylphenyl) pentaerythrityl diphosphite,2,2′-ethylidenebis(2,4-di-tert-butylphenyl) fluorophosphite or2-butyl-2-ethylpropan-1,3-diyl 2,4,6-tri-tert-butylphenyl phosphite.

Still other preferred compositions are those wherein the additionalstabilizer is a benzofuran-2-one; preferably5,7-di-tert-butyl-3-(3,4-dimethyl phenyl)-2H-benzofuran-2-one.

Still other preferred composition are those wherein the additionalstabilizer is a metal chelating agent; preferably citric acid, ketoacids, gluconates, heptagluconates, phosphates, phosphonates andaminocarboxylic acid chelates, such as ethylenediaminetetraacetic acid(EDTA), diethylenetriaminepentaacetic acid (DTPA),hydroxyethylethlenediaminetriacetic acid (HEDTA), nitrilotriacetic acid(NTA) and diethylenetriaminepentamethylenephosphonic acid (DTPMPA).

Some preferred compositions contain a mixture of additional stabilizerssuch as a mixture of a UV absorber and polymeric inhibitor; or a mixtureof a UV absorber and a sulfur containing compound; or a mixture of a UVabsorber and a phosphorus containing compound; or a mixture of a UVabsorber and a metal chelating agent; or a mixture of a polymericinhibitor and a sulfur containing compound; or a mixture of a polymericinhibitor and a phosphorus containing compound; or a mixture of a sulfurcontaining compound and a phosphorus containing compound; or a mixtureof a UV absorber, a polymeric inhibitor and a sulfur containingcompound; or a mixture of a UV absorber, a polymeric inhibitor and aphosphorus containing compound; or a mixture of a UV absorber, apolymeric inhibitor, a sulfur containing compound and a phosphoruscontaining compound; or a mixture of a UV absorber, a polymericinhibitor and a metal chelating agent.

Some preferred composition are those wherein the additional stabilizeris a mixture of a hindered amine hydroxylamine with at least one opticalbrightener such as2,2′-[(1,1′-diphenyl)-4,4′-diyl-1,2-ethenediyl]bis-benzenesulfonic,disodium salt {or bis[4,4′-(2-stilbenesulfonic acid)], disodium salt}which is TINOPAL® SK, Ciba.

Preferably the compositions are those wherein the compound of formula I,II, III, IA, IIA or IIIA is of low molecular weight or containshydrophilic moieties or is both of low molecular weight and containshydrophilic moieties.

The instant inhibitor additive system can be added to pulp or paper at anumber of places during the manufacturing or processing operations.These include

-   -   a. on a pulp slurry in the latency chest;    -   b. on a pulp slurry in or after the bleaching stage in a        storage, blending or transfer chest;    -   c. on pulp during or after bleaching, washing and dewatering        followed by cylinder or flash drying;    -   d. before or after the cleaners;    -   e. before or after the fan pump to the paper machine headbox;    -   f. to the paper machine white water;    -   g. to the silo or save all;    -   h. in the press section using a size press, coater or spray bar;    -   i. in the drying section using a size press, coater or spray        bar;    -   j. on the calender using a wafer box;    -   k. on paper in an off-machine coater or size press; and/or    -   l. in the curl control unit.

Clearly, the precise location where the stabilizer additives should beadded will depend on the specific equipment involved, the exact processconditions being used and the like. In some cases, the additives may beadded at one or more locations for most effectiveness.

If the stabilizer or other coadditives are not themselves“water-soluble”, they may be dispersed or emulsified by standard methodsprior to application. Alternatively, the stabilizer and/or coadditivesmay be formulated into a paper sizing or paper coating formulation.

Stabilizers of present invention are also active as light stabilizersfor organic materials, especially organic polymers. Thus, they may beappliad with advantage in bulk polymers such as polyolefins, films,fibers, or in coatings. Substrates, coadditives and specific ways ofapplication for this purpose include those known in the art, e.g. asdescribed in U.S. Pat. No. 5,948,836 column 3, line 37, until column 9,line 61 (substrates); col. 1, line 46, until col. 3, line 36, and col.17, line 65, until col. 25, line 30 (coadditives); and col. 17, lines39–61, col. 26, lines 33–39, and the same col. 26, line 52, until col.27, line 18, and col. 28, lines 11–17 (methods of application).

The following examples are for illustrative purposes only and are not tobe construed to limit the instant invention in any manner whatsoever.

Handsheet Treatment

All additives are applied by syringe-injecting the appropriate weight %of additive combination in either an aqueous solution when the additiveis water soluble, or a solution in 1:1 ethanol/dioxane, onto bleachedthermomechanical pulp (BTMP) brightness squares (4 cm×4 cm). The clampedsheets are allowed to air dry for one day.

The brightness of the handsheets is recorded before and after treatmentby light exposure under controled intensity conditions.

Accelerated testing is carried out by subjecting the treated sheets toaccelerated light induced yellowing in a fan-cooled light box containingeight fluorescent lamps with a spectral maximum output at 5700 Å with atotal output approximately 43 times greater than normal officefluorescent lamps. The lamps are about ten inches away from thehandsheets being illuminated.

Ambient testing is carried out by placing the treated handsheets on adesk under normal cool-white fluorescent office lights at a nominaldistance of six feet.

In both cases, ISO brightness is tracked as a function of photolysistime and converted to post color number (PC number) in the usual manner.

Post color (PC) number is defined as follows:

-   -   PC=[(k/s)_(after)−(k/s)_(before)]×100    -   k/s=(1−R_(inf))²/2 R_(inf)        where k and s are the absorption and scattering coefficients,        respectively, and R_(inf) is the value of ISO brightness.

The relationship between R_(inf) and the chromophore concentration isnon-linear, whereas, the PC number is roughly linearly related to theconcentration of the chromophore in the sample.

Low PC numbers are desired as they indicate less yellowing.

When, using the ambient test conditions, untreated BTMP handsheets arecompared to Kraft handsheets after 60 days, the BTMP handsheets have aPC number which is about 10 while the Kraft paper has a PC number whichis about 0.39. The Kraft handsheets are clearly less yellow thanuntreated BTMP handsheets after exposure to ambient light.

The incident light flux for the accelerated yellowing experiments(Examples 1–10) is 43 times greater than normal office fluorescent lampsas measured by the A. W. Speery SLM-110 digital light power meter. Thebrightness of the handsheets is tracked and compared to that ofuntreated sheets exposed in the same manner. The treated sheets exhibitsignificant resistance to yellowing as is seen below.

EXAMPLE 1

8-Oxyl-7,7,9,9-tetramethyl-1,3,8-triaza-spiro[4.5]decane-2,4-dione

The titled compound is synthesized by the procedure of L. Dulog and R.Seidemann, Makromol. Chem. 187, 2545 (1986).

EXAMPLE 28-Oxyl-7,7,9,9-tetramethyl-3-oxiranylmethyl-1,3,8-triaza-spiro[4.5]decane-2,4-dione

To a solution of 2.0 g (8.3 mmol) of the compound of example 1 and 0.4 g(10 mmol) sodium hydroxide dissolved in 17 ml of water is added 0.92 g(10 mmol) epichlorohydrin. The reaction mixture is stirred at roomtemperature for 6 hrs. The mixture is partitioned between water andethyl acetate. The organic phase is dried and concentrated. Purificationby column chromatography yields the product as a red solid: mp 154° C.

EXAMPLE 3

[2-Hydroxy-3-(8-oxyl-7,7,9,9-tetramethyl-2,4-dioxo-1,3,8-triaza-spiro[4.5]dec-3-yl)-propyl]-trimethyl-ammoniumchloride

The compound in Example 2 is reacted with aqueous trimethylamine. Oneequivalent of hydrochloric acid is added to yield the titled compound.

EXAMPLE 4 N-Butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidine

A 0.5 LParr hydrogenation bottle is charged with 10.3 g (55.6 mmol) of1-methoxy-2,2,6,6-tetramethylpiperid-4-one, 8.0 g (110 mmol) n-butylamine, 1.0 g 8% Pd, 2% Pt on carbon hydrogenation catalyst and 100 mL ofisopropanol. The bottle is pressurized with 50 PSI of hydrogen andshaken for 4 hours. The catalyst is removed by filtration and thesolvent and excess amine is removed by evaporation under reducedpressure. 11.0 g of the title compound is isolated as a colorless oilafter column chromatography. ¹H NMR (CDCL₃) δ 0.91 (t, 3H), 1.12 (s,6H), 1.19 (s, 6H), 1.25 (t, 2H), 1.34 (m, 2H), 1.46 (q, 2H), 1.73 (d,2H), 2.60 (t, 2H), 2.77 (tt, 1H), 3.60 (s, 3H).

EXAMPLE 5N-Butyl-N-(2-hydroxy-3-chloro)propyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidine

A solution of 5.0 g (20.6 mmol) ofN-butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidine (Example 4)dissolved in 20 mL of epichlorohydrin is stirred for 48 hours at roomtemperature. The excess epichlorohydrin is removed by distillation andthe title compound is isolated as a colorless oil after columnchromatography. MS m/z 335 (M+H).

EXAMPLE 6

N-Butyl-N-(2-hydroxy-3-chloro)propyl-1-oxyl-2,2,6,6-tetramethyl-4-aminopiperidine

The title compound is prepared according to the procedure of Example 5by replacing N-butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidinewith N-butyl-1-oxyl-2,2,6,6-tetramethyl-4-aminopiperidine.

EXAMPLE 6AN-Butyl-N-(2-hydroxy-3-chloro)propyl-1-hydroxy-2,2,6,6-tetramethyl-4-aminopiperidine

The title compound is prepared according to the procedure of Example 5by replacing N-butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidinewith N-butyl-1-hydroxy-2,2,6,6-tetramethyl-4-aminopiperidine.

EXAMPLE 7N,N′-Bis-(2-hydroxy-3-chloro)propyl-N,N′-bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-1,6-diaminohexane

The title compound is prepared according to the method of Example 5 byreplacing N-butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidine withN,N′-bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-1,6-diaminohexane.

EXAMPLE 7AN,N′-Bis-(2-hydroxy-3-chloro)propyl-N,N′-bis(1-hydroxy-2,2,6,6-tetramethyl-piperidin-4-yl)-1,6-diaminohexane

The title compound is prepared according to the method of Example 5 byreplacing N-butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidine withN,N′-bis(1-hydroxy-2,2,6,6-tetramethyl-piperidin-4-yl)-1,6-diaminohexane.

EXAMPLE 81-Butyl-1-(1-methoxy-2,2,6,6-tetramethyl-piperidin-4-yl)-3-hydroxy-azetidiniumChloride

The compound of Example 5 is heated at 100° C. in water for 2 hours toform the title compound as an equal mixture of diastereomers. ¹H NMR(D₂O) δ 0.99 (t, 3H), 1.25 (s, 3H), 1.26 (s, 3H), 1.35 (s, 6H), 1.43 (m,2H), 1.68–1.84(m, 4H), 2.03 (m, 2H), 3.32 & 3.56 (t, 2H), 3.64 & 3.83(br t, 1H), 3.70 (s, 3H), 4.13, 4.30, 4.50 & 4.70 (dd, 4H), 4.71 & 4.84(m, 1H).

EXAMPLE 91-Butyl-1-(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yl)-3-hydroxy-azetidiniumChloride

The compound of Example 6 is heated at 100° C. in water to form thetitle compound as an equal mixture of diastereomers. ¹H NMR (CD₃OD) δ0.98 (t, 3H), 1.14 (s, 3H), 1.15 (s, 3H), 1.20 (s, 6H), 1.39 (q, 2H),1.56–1.78 (m 4H), 1.84–1.95 (m, 2H), 3.20 & 3.44 (t, 2H), 3.53 & 3.72(br t, 1H), 3.98, 4.15, 4.40, (dd, 3H), 4.53–4.72 (c, 2H). ¹³C NMR(CD₃OD) δ 69.8 (CH₂), 69.5 (CH₂), 59.3 (CH), 58.8 (CH), 38.5 (CH₂), 38.3(CH₂), 32.8 (CH₃), 26.2 (CH₂), 25.9 (CH₂), 20.8 (CH₂), 20.0 (CH₃).

EXAMPLE 9A1-Butyl-1-(1-hydroxy-2,2,6,6-tetramethyl-piperidin-4-yl)-3-hydroxy-azetidiniumChloride

The compound of Example 6A is heated at 100° C. in water to form thetitle compound as an equal mixture of diastereomers.

EXAMPLE 10N,N′-Bis(1-hydroxy-2,2,6,6-tetramethyl-piperidin-4-yl)-1,6-bis(3-hydroxyazetidinium)hexane

The compound of Example 7A is heated at 100° C. in water to form thetitle compound.

EXAMPLE 11

4-(3-Butylamino-2-hydroxy-propoxy)-2,2,6,6-tetramethyl-piperidin-1-oxyl

To a solution of 6.3 g (0.086 moles) n-butylamine dissolved in 50 mL ofwater is added 6.0 g (0.026 moles)1-oxyl-2,2,6,6-tetramethyl-4-glycidyloxypiperidine (U.S. Pat. No.6,080,864). The mixture is vigorously stirred for 24 hours and thenpartitioned between water and ethyl acetate. The organic phase is driedover sodium sulfate and concentrated under reduce pressure to yield thetitle compound as a red oil.

EXAMPLE 12

4-{3-[Butyl-(3-chloro-2-hydroxy-propyl)-amino]-2-hydroxy-propoxy}-2,2,6,6-tetramethyl-piperidin-1-oxyl

The title compound is prepared according to the procedure of Example 5by replacing N-butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidinewith the compound of Example 11.

EXAMPLE 12A

4-{3-[Butyl-(3-chloro-2-hydroxy-propyl)-amino]-2-hydroxy-propoxy}-2,2,6,6-tetramethyl-piperidin-1-ol

The title compound is prepared according to the procedure of Example 5by replacing N-butyl-1-methoxy-2,2,6,6-tetramethyl-4-aminopiperidinewith4-(3-Butylamino-2-hydroxy-propoxy)-2,2,6,6-tetramethyl-piperidin-1-ol.

EXAMPLE 13

1-Butyl-3-hydroxy-1-[2-hydroxy-3-(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yloxy)-propyl]-azetidiniumchloride

The compound of Example 12 is heated at 100° C. in water to form thetitle compound.

EXAMPLE 13A

1-Butyl-3-hydroxy-1-[2-hydroxy-3-(1-hydroxy-2,2,6,6-tetramethyl-piperidin-4-yloxy)-propyl]-azetidiniumchloride

The compound of Example 12A is heated at 100° C. in water to form thetitle compound.

EXAMPLE 144-(2-Dimethylamino)ethoxy-1-oxyl-2,2,6,6-tetramethylpiperidine

To a two-phase mixture of 10 mL of 50% aqueous sodium hydroxide and 3 mLof toluene is added 0.26 g (0.8 mmol) of tetrabutylammonium bromide, 3.0g (17.4 mmol) of 1-oxyl-4-hydroxy-2,2,6,6-tetramethylpiperidine and 2.5g (17.4 mmol) of 2-dimethylaminoethyl chloride hydrochloride. Themixture is stirred vigorously at 70° C. for five hours. The reactionmixture is then partitioned between water and ethyl acetate. The organicphase is washed with water and dried over anhydrous sodium sulfate.Removal of the solvent leaves a red oil from which the title compound isisolated as a red oil by column chromatography.

EXAMPLE 154-(2-Dimethylamino)ethoxy-1-hydroxy-2,2,6,6-tetramethylpiperidine

A 0.5 L Parr bottle is charged with 2.0 g (8.2 mmol)4-(2-Dimethylamino)ethoxy-1-oxyl-2,2,6,6-tetramethylpiperidine (Example14), 100 mg 5% Pt on C hydrogenation catalyst and 100 mL of methanol.The bottle is pressurized to 50 psi with hydrogen and shaken for 30minutes. The catalyst is removed by filtration and the methanol isremoved by evaporation under reduced pressure to yield the titledcompound as a pale yellow viscous oil. ¹H NMR (CDCL₃) δ 1.15 (s, 6H),1.20 (s, 6H), 1.45 (t, 2H), 1.92 (d, 2H), 2.41 (s, 6H), 2.65 (t, 2H),3.59 (tt, 1H), 3.64 (t, 2H).

EXAMPLE 164-(2-Dimethylpropylammonium)ethoxy-1-oxyl-2,2,6,6-tetramethylpiperidinebromide

A solution of 5.0 g (20.5 mmol) of4-(2-Dimethylamino)ethoxy-1-oxyl-2,2,6,6-tetramethylpiperidine (Example14) and 5.05 g (41 mmol) propyl bromide dissolved in 25 mL of ethanol isrefluxed for 3 hours. The solvent is evaporated under reduced pressure,the residue is washed with ethyl acetate and then dried under vacuum toyield 6.5 g of the product as a red oil. MS-FAB m/z 287 (M ion minus Brand plus H).

EXAMPLE 174-(2-Dimethylpropylammonium)ethoxy-1-hydroxy-2,2,6,6-tetramethylpiperidinebromide

The title compound is prepared according to the procedure of Example 15by replacing4-(2-Dimethylamino)ethoxy-1-oxyl-2,2,6,6-tetramethylpiperidine with4-(2-Dimethylpropylammonium)ethoxy-1-oxyl-2,2,6,6-tetramethylpiperidinebromide. A pale yellow viscous oil is obtained. ¹H NMR (CD₃OH) δ 0.99(t, 3H), 1.15 (s, 6H), 1.18 (s, 6H), 1.41 (t, 2H), 1.80 (m, 2H), 1.95(d, 2H), 3.11 (s, 6H), 3.31 (m, 2H), 3.52 (br t, 2H), 3.71 (tt, 1H),3.87 (br m, 2 H).

EXAMPLE 18N,N,N′,N′-Tetramethyl-N,N′-bis-[2-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxy)-ethyl]-hexamethylenediammoniumDibromide

The title compound is prepared according to the procedure of Example 16by replacing propyl bromide with 1,6-dibromohexane. A red oil isobtained. MS-FAB m/z 651 (M ion minus Br and plus 2H).

EXAMPLE 191,7-Bis-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)1,4,7-triazaheptane

A Parr shaker bottle containing 20.0 g (0.117 mol)1-oxyl-2,2,6,6-tetramethylpiperidin-4-one, 6.0 g (0.058 mol)diethylenetriamine, 0.5 g 8% Pt/2% Pd on Carbon and 120 mL methanol ispressurized with hydrogen and shaken for 2 hours. The catalyst isremoved by filtration and the solution is concentrated to 40 mL. Theproduct is precipitates as a white solid with the addition of 200 mL ofethyl ether: mp 118–124° C.

EXAMPLE 20

The compound of Example 19 is reacted with one to four equivalents of2,3-epoxypropyl-trimethylammonium chloride to yield a water solublehydroxylamine.

EXAMPLE 21 Accelerated Yellowing with High Intensity Lamps

A sheet consisting of 75% bleached mechanical fibers and 25% bleachedkraft is treated with 1.0% by weight of a test compound from Examples14, 15, 16 and 17 and exposed to accelerated aging as described above.The sheets treated with these novel additives exhibit substantialinhibition of yellowing compared to the untreated control sheet.

EXAMPLE 22 Accelerated Yellowing with High Intensity Lamps

A sheet consisting of 75% bleached mechanical fibers and 25% bleachedkraft is treated with 1.0% by weight of a test compound from Examples14, 15, 16 and 17 and 0.5% by weight of Cibafast W, a UV absorber. Thesheets treated with these novel additives and a UV absorber exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when a combination ofinstant compound with a UV absorber is used.

EXAMPLE 23 Accelerated Yellowing with High Intensity Lamps

A BTMP sheet is treated with 1.0% by weight of a test compound fromExamples 14, 15, 16 and 17 and 0.5% by weight of citric acid, a metalchelating agent. The sheets treated with these novel polymeric additivematerials and a metal chelating agent exhibit substantial inhibition toyellowing compared to the untreated control sheet and illustrate theperformance enhancement when a combination of instant compound with ametal chelating agent is used.

EXAMPLE 24 Accelerated Yellowing with High Intensity Lamps

A BTMP sheet is treated with 1.0% by weight of a test compound fromExamples 3 to 20 and 0.5% by weight of a UV absorber. The sheets treatedwith these novel polymeric additive materials and a UV absorber exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when a combination ofinstant compound with a UV absorber is used.

EXAMPLE 25 Accelerated Yellowing with High Intensity Lamps

A BTMP sheet is treated with 1.0% by weight of a test compound fromExamples 3 to 20 and 0.5% by weight of a metal chelating agent. Thesheets treated with these novel polymeric additive materials and a metalchelating agent exhibit substantial inhibition to yellowing compared tothe untreated control sheet and illustrate the performance enhancementwhen a combination of instant compound with a metal chelating agent isused.

EXAMPLE 26 Accelerated Yellowing with High Intensity Lamps

A BTMP sheet is treated with 1.0% by weight of a test compound fromExamples 3 to 20 and 0.5% by weight of a fluorescent whitening agent.The sheets treated with these novel polymeric additive materials and afluorescent whitening agent exhibit substantial inhibition to yellowingcompared to the untreated control sheet and illustrate the performanceenhancement when a combination of instant compound with a fluorescentwhitening agent is used.

1. A compound of formula VIII or VIIIA

where n is 1 or 2 and m ranges from 2 to 6; E is oxyl, hydroxyl,hydrogen, alkyl, alkyl substituted by hydroxyl, by oxo or by carboxy,alkyl interrupted by oxygen, by —COO— or by —OCO—, alkenyl, alkynyl,cycloalkyl, cycloalkenyl, bicycloalkyl, alkoxy, alkoxy substituted byhydroxyl, by oxo or by carboxy, alkoxy interrupted by oxygen, by —COO—or by —OCO—, cycloalkoxy, alkenyloxy, cycloalkenyloxy, aralkyl,aralkoxy, acyl, RCOO—, ROCOO—, RNCOO— or chloro where R is an aliphaticor aromatic moiety, when n is 1, R₁ is hydrogen, alkyl of 1 to 18 carbonatoms, alkenyl of 2 to 18 carbon atoms, propargyl, glycidyl, alkyl of 2to 50 carbon atoms interrupted by one to twenty oxygen atoms, alkyl of 2to 50 carbon atoms substituted by one to ten hydroxyl groups or bothinterrupted by said oxygen atoms and substituted by said hydroxylgroups, or R₁ is alkyl of 1 to 4 carbon atoms substituted by a carboxygroup or by —COOZ where Z is hydrogen, alkyl of 1 to 4 carbon atoms orphenyl, or where Z is said alkyl substituted by —(COO⁻)_(n)M^(n+) wheren is 1–3 and M is a metal ion from the 1st, 2nd or 3rd group of theperiodic table or is Zn, Cu, Ni or Co, or M is a group N^(n+) (R₂)₄where R₂ is hydrogen, alkyl of 1 to 8 carbon atoms or benzyl, or when nis 2, R₁ is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12carbon atoms, xylylene or alkylene of 1 to 50 carbon atoms interruptedby one to twenty oxygen atoms, substituted by one to ten hydroxyl groupsor both interrupted by said oxygen atoms and substituted by saidhydroxyl groups, X is an inorganic or organic anion, where the index jequals the number of ammonium ions in the formula divided by the valencyof X; and the total charge of cations is equal to the total charge ofanions.
 2. A compound according to claim 1 wherein the anion X isphosphate, phosphonate, carbonate, bicarbonate, nitrate, chloride,bromide, iodide bisulfite, sulfite, bisulfate, sulfate, borate, formate,acetate, benzoate, citrate, oxalate, tartrate, acrylate, polyacrylate,fumarate, maleate, itaconate, glycolate, gluconate, malate, mandelate,tiglate, ascorbate, polymethacrylate, a carboxylate of nitrilotriaceticacid, hydroxyethylethylenediaminetriacetic acid,ethylenediaminetetraacetic acid or of diethylenetriaminepentaaceticacid, a diethylenediaminetetraacetic acid or ofdiethylenetriaminepentaacetic acid, an alkylsulfonate or anarylsulfonate.
 3. A compound according to claim 1 wherein E is selectedfrom oxyl, hydroxyl, C₁–C₁₈alkoxy; C₃–C₁₈alkoxy substituted by hydroxyl,oxo or carboxy or interrupted by oxygen or carboxy; C₅–C₁₂cycloalkoxy;C₃–C₁₂alkenyloxy; cyclohexenyloxy; aralkyl or aralkoxy of 7 to 15 carbonatoms; C₁–C₁₂ acyl; R(C═O)O—, RO(C═O)O—, RN(C═O)O—, where R isC₁–C₁₈alkyl, phenyl, C₇–C₁₅phenylalkyl, cyclohexyl, C₂–C₃alkenyl.
 4. Acompound according to claim 1 of formula VIII.
 5. A compound accordingto claim 4, wherein m is 2 or 3; E is oxyl, hydroxyl, or C₁–C₈alkyl; R₁,when n is 1, is H or C₁–C₈alkyl, or, when n is 2, is alkylene of 2–12carbon atoms; and X is chloride, bromide or citrate.